REM sleep is a behavioral state of all mammalian organisms, including humans, which is controlled by active neuronal mechanisms in the pontine brain stem. Identification of the several generator population(s) involved and the means by which such populations are simultaneously (or sequentially) activated are still imprecisely detailed. The problem is an important one for behavioral neurobiology whose solution could shed light on the pathogenesis of sleep disorders, elucidate the physiological basis of human dreaming, and provide models for understanding the perceptual, cognitive, and emotional disturbances of mental illnesses. Single-cell recording and drug microinjection studies suggest that REM sleep is cholinergically enhanced and, reciprocally, aminergically suppressed. In addition to our new pharmacological experiments designed to test this reciprocal interaction model of REM sleep control, we will apply two newly developed techniques to more clearly define cellular and molecular details of REM-sleep generation in cats. Most of our proposed studies build upon our capacity to induce a REM sleep-like state by microinjecting cholinergic agonists into the pontine brain stem. The new techniques are: (1) carbachol-conjugated fluorescent microspheres to delimit the effective drug injection site and retrogradely label afferent neuronal populations projecting to it, and (2) a microinjector- microelectrode system allowing neuronal activity to be recorded at the effective site for, during, and after carbachol administration. The cholinergic REM-induction technique will be combined with the new methods as a tool to clarify such questions as: (1) What are the anatomical and physiological properties of neurons at the REM sleep induction site? (2) What are the afferent projections to the site, especially from known cholinergic and aminergic neuronal groups? We will also explore aminergic predictions of the model with new pharmacological studies designed to follow up on the observed enhancement of REM sleep following beta adrenergic blockade of the reticular formation; the cellular response of aminergic neurons to pharmacological REM sleep induction will also be determined. The concepts, methods and results of this work should not only advance sleep research, but also find application in other areas of behavioral neurobiology.